Bond strength of Ti–5Cr based alloys to dental porcelain with Mo addition

Porcelain fused to metal crown (PFM) is widely used in dental restoration for its esthetics. Due to its excellent corrosion resistance, biocompatibility and mechanical properties, commercially pure titanium (c.p. Ti) and Ti–6Al–4V alloy have dramatically improved dental implants and prosthesis, despite the insufficient bond strength of titanium to porcelain. This study investigated the bond strength of new Ti–5Cr–xMo (x = 1–11 wt.%) alloys and low-fusing dental porcelain (Duceratin Plus, DeguDent Gmbh, Germany), and c.p. Ti and Ti–6Al–4V alloy were compared. The results show that Ti–5Cr–9Mo alloy has the highest bond strength (37.67 MPa), a result that is higher than that of c.p. Ti (30.72 MPa) and Ti–6Al–4V (30.01 MPa).     

Effects of Si addition on microstructure and mechanical properties of Mg–8Gd–4Y–Nd–Zr alloy

Effects of Si addition (1.0 wt.%) on microstructure and mechanical properties of Mg–8Gd–4Y–Nd–Zr alloy have been investigated using scanning electron microscopy (SEM) equipped with energy dispersive spectrum (EDS), X-ray diffraction (XRD), hardness measurements and tensile testing. The results indicated that the addition of Si led to the formation of Mg₂Si and (RE + Si)-rich particles, which enhanced the Young’s modulus of the alloy by 7 GPa while decreased the yield strength and ultimate strength by 10 MPa and 31 MPa, respectively. The tensile properties of the Mg–8Gd–4Y–Nd–Zr–Si alloy are as follows: Young’s modulus E = 51 GPa, yield strength σ_0.2 = 347 MPa, ultimate strength σ_b = 392 MPa and elongation δ = 2.7%. The increase in Young’s modulus was attributed to the formation of particles with high Young’s modulus, while the decrease in strength was ascribed to the decrease in volume fraction of metastable β′ precipitates caused by the consumption of rare earth atoms due to the formation of the rare earth containing particles.     

Creep deformation and crack growth rates of a super α2 titanium aluminide alloy

The influences of stress and temperature on creep deformation behavior and the creep crack growth rates of the super α₂ Ti₃Al alloy were investigated with respect to its safe application at high temperatures. In a temperature range of 1033–1093 K at low applied stress levels, the stress exponent was equal to 1.5. At an intermediate stress range (10^?3 < σ/E < 3 × 10^?3), a stress exponent of 3.3 was observed. As the applied stress was increased, the stress exponent changed from 3.3 to 4.4. The high temperature crack growth rate of the Ti₃Al alloy can be correlated with stress intensity factor K rather than C1 at 1033 K due to environmental embrittlement.     

Mechanical properties of Ti–4.5Al–3V–2Mo–2Fe and possibility for healthcare applications

The mechanical properties of Ti–4.5Al–3V–2Mo–2Fe, a relatively low cost titanium alloy originally designed for structural applications (especially for aerospace applications), were investigated. The alloy was subjected to heat treatments with various solution treatment temperatures (annealing temperature) and cooling rates. The mechanical properties of the heat-treated alloys were then used in order to judge the prospects of practical usage of the alloy for healthcare equipment such as wheelchairs.The mechanical properties of Ti–4.5Al–3V–2Mo–2Fe are highly affected by either solution treatment or cooling rate, and they change as a result of the change in the microstructure. The alloy single annealed at temperature in the α + β field has very high fatigue ratio (0.80–0.85) and high specific strength (210–260 MPa/g cm^− 3) with a modest fracture toughness (J_IC = 25–35 kN/m). This balance of fatigue ratio and specific strength is better than that of the existing wheelchair materials.Thus, from the point of view of mechanical properties, Ti–4.5Al–3V–2Mo–2Fe has high potential to be used for healthcare applications.     

Effects of processing parameters on microstructure and mechanical properties of squeeze-cast Mg–12Zn–4Al–0.5Ca alloy

In this paper, a new magnesium alloy Mg–12Zn–4Al–0.5Ca (ZAX12405) was prepared by squeeze casting. The effects of processing parameters including applied pressure, pouring temperature and dwell time on the microstructure and mechanical properties of squeeze-cast ZAX12405 alloy were investigated. It was found that squeeze-cast ZAX12405 alloy exhibited finer microstructure and much better mechanical properties than gravity casting alloy. Increasing the applied pressure led to significant cast densification and a certain extent of grain refinement in the microstructure, along with obvious promotion in mechanical properties. Lowering the pouring temperature refined the microstructure of ZAX12405 alloy, but deteriorated the cast densification, resulting in that the mechanical properties firstly increased and then decreased. Increasing the dwell time promoted cast densification and mechanical properties just before the solidification process ended. A combination of highest applied pressure (120 MPa), medium pouring temperature (650 °C) and dwell time (30 s) brought the highest mechanical properties, under which the ultimate tensile strength (UTS), yield strength (YS) and elongation to failure (E_f) of the alloy reached 211 MPa, 113 MPa and 5.2% at room temperature. Comparing with the gravity casting ZAX12405 alloy, the UTS and E_f increased 40% and 300%, respectively. For squeeze-cast Mg–12Zn–4Al–0.5Ca alloy, cast densification was considered more important than microstructure refinement for the promotion of mechanical properties.     

Transformation behavior and shape memory characteristics of thermo-mechanically treated Ti–(45−x)Ni–5Cu–xV (at%) alloys

Transformation behavior, shape memory characteristics and superelasticity of thermo-mechanically treated Ti–(45?x)Ni–5Cu–xV (at%) (x = 0.5–2.0) alloys were investigated by means of differential scanning calorimetry, transmission electron microscopy, X-ray diffractions, thermal cycling tests under constant load and tensile tests. The B2–B19′ transformation occurred when V content was 0.5 at%, above which the B2–B19–B19′ transformation occurred. The B2–B19 transformation was not separated clearly from the B19–B19′ transformation. Thermo-mechanically treated Ti–(45?x)Ni–5Cu–xV alloys showed perfect shape memory effect and transformation hysteresis(ΔT) of Ti–43.5Ni–5.0Cu–1.5V and Ti–43.0Ni–5.0Cu–2.0V alloys was about 9 K which was much smaller than that of a Ti–44.5Ni–5.0Cu–0.5V alloy(23.3 K). More than 90% of superelastic recovery ratio was observed in all specimens and transformation hysteresis (Δσ) of a Ti–44.5Ni–5.0Cu–0.5V alloy was about 70 MPa, which was much larger than that of a Ti–43.0Ni–5.0Cu–2.0V alloy (35 MPa).     

Effect of in situ synthesized TiB whisker on microstructure and mechanical properties of carbon–carbon composite and TiBw/Ti–6Al–4V composite joint

Carbon–carbon composite (C–C composite) and TiB whiskers reinforced Ti–6Al–4V composite (TiB_w/Ti–6Al–4V composite) were brazed by Cu–Ni + TiB₂ composite filler. TiB₂ powders have reacted with Ti which diffused from TiB_w/Ti–6Al–4V composite, leading to formation of TiB whiskers in the brazing layer. The effects of TiB₂ addition, brazing temperature, and holding time on microstructure and shear strength of the brazed joints were investigated. The results indicate that in situ synthesized TiB whiskers uniformly distributed in the joints, which not only provided reinforcing effects, but also lowered residual thermal stress of the joints. As for each brazing temperature or holding time, the joint shear strength brazed with Cu–Ni alloy was lower than that of the joints brazed with Cu–Ni + TiB₂ alloy powder. The maximum shear strengths of the joints brazed with Cu–Ni + TiB₂ alloy powder was 18.5 MPa with the brazing temperature of 1223 K for 10 min, which was 56% higher than that of the joints brazed with Cu–Ni alloy powder.     

Effect of Zn addition,strain rate and deformation temperature on the tensile properties of Sn–3.3 wt.% Ag solder alloy

Stress–strain characteristics of the binary Sn–3.3 wt.% Ag and the tertiary Sn–3.3 wt.% Ag–1 wt.% Zn solder alloys were investigated at various strain rates (SR, ε^·) from 2.6 × 10^− 4 to 1.0 × 10^− 2 s^− 1 and deformation temperatures from 300 to 373 K. Addition of 1 wt.% Zn to the binary alloy increased the yield stress σ_y and the ultimate tensile stress σ_UTS while a decrease of ductility (total elongation ε_T) was observed. Increasing the strain rate (ε^·) increased both σ_y and σ_UTS according to the power law σ = C ε^·m. A normal decrease of ε_T with strain rate was observed according to an empirical equation of the form ε_T = A exp (− λε^·); A and λ are constants. Increasing the deformation temperature decreased both σ_y and σ_UTS in both alloys, and decreased the total elongation ε_T in the Zn-free binary alloy, whereas ε_T was increased in the Zn-containing alloy. The activation energy was determined as 41 and 20 kJ mol^− 1 for these alloys, respectively. The results obtained were interpreted in terms of the variation of the internal microstructure in both alloys. The internal microstructural variations in the present study were evaluated by optical microscopy, electron microscopy and X-ray diffraction. The results show the importance of Zn addition in enhancing the mechanical strength of the Sn–3.3 wt.% Ag base alloy.     

Effects of Al content on structure and mechanical properties of hot-rolled ZrTiAlV alloys

Zirconium alloys show attractive properties for astronautic applications where the most important factors are anti-irradiation, corrosion resistance, anti-oxidant, very good strength-to-weight ratio. The effects of Al content (2.2–6.9 wt%) on structure and mechanical properties of the hot-rolled ZrTiAlV alloy samples were investigated in this study. Each sample of the hot-rolled ZrTiAlV alloys with Al contents from 2.2 wt% to 5.6 wt% is composed of the α phase and β phase, meanwhile, the relative content of the α phase increased with the Al content. However, the (ZrTi)₃Al intermetallic compound was observed as the Al content increased to 6.9 wt%. Changes of phase compositions and structure with Al content distinctly affected mechanical properties of ZrTiAlV alloys. Yield strength of the alloy with 2.2 wt% Al is below 200 MPa. As Al content increased to 5.6 wt%, the yield strength, tensile strength and elongation of the examined alloy are 1088 MPa, 1256 MPa and 8%, respectively. As Al content further increased to 6.9 wt%, a rapid decrease in ductility was observed as soon as the (ZrTi)₃Al intermetallic compound precipitated. Results show that the ZrTiAlV alloys with Al contents between 3.3 wt% and 5.6 wt% have excellent mechanical properties.     

Effect of (α + β) heat treatment on microstructure and mechanical properties of (TiB + TiC)/Ti–B20 matrix composite

For the first stage, a metastable β titanium alloy, Ti–3.5Al–5Mo–4V–2Cr–2Sn–2Zr–1Fe reinforced with trace amounts of TiB whiskers and TiC particles was fabricated by vacuum arc melting process and hot forging followed by heat treatment at 780 °C/740 °C, then by aging at 500 °C, 550 °C, 570 °C and 600 °C. For the second stage, the unreinforced titanium alloy was also fabricated by the same process. The microstructural characteristics were investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Traces of TiB whiskers and TiC particles (2.2 vol.%) with a volume ratio of 2:3 synthesized in situ exerted a hybrid reinforcing effect on the β titanium alloy. The reinforcements were uniformly distributed in the matrix and the elastic modulus was improved about 25 GPa. Ultimate tensile strength and yield strength achieves about 1625 MPa and 1500MPa respectively, with ductility at 7% when the aging temperature is 500 °C. The ductility of (TiB + TiC)/(Ti–3.5Al–5Mo–4 V–2Cr–2Sn–2Zr–1Fe) matrix composite could be enhanced by increasing the aging temperatures. After 780 °C followed by aging at 570 °C, excellent strength and plasticity properties were obtained (ultimate tensile strength of matrix alloy is 1350 MPa with elongation of 18% and ultimate tensile strength of composite is 1500 MPa with elongation of 13%).     

Surface treatment of new type aluminum lithium alloy and fatigue crack behaviors of this alloy plate bonded with Ti–6Al–4V alloy strap

Samples consisting of new aluminum lithium alloy (Al–Li alloy) plate developed by the Aluminum Company of America and Ti–6Al–4V alloy (Ti alloy) plate were investigated. Plate of 400 mm × 140 mm × 2 mm with single edge notch was anodized in phosphoric solution and Ti alloy plate of 200 mm × 20 (40) mm × 2 mm was anodized in alkali solution. Patterns of two alloys were studied at original/anodized condition. And then, aluminum alloy and Ti alloy plates were assembled into a sample with FM 94 film adhesive. Fatigue crack behaviors of the sample were investigated under condition of nominal stress σ = 36 MPa and 54 MPa, stress ratio of 0.1. Testing results show that anodization treatment modifies alloys surface topography. Ti alloy bonding to Al–Li alloy plate effectively retards crack growth than that of Al–Li alloy plate. Fatigue life of sample bonded with Ti alloy strap improves about 62.5% than that of non-strap plate.     

Investigation of glass-forming ability,deformation and corrosion behavior of Ni-free Ti-based BMG alloys designed for application as dental implants

We developed new Ti-based bulk metallic glassy (BMG) alloys in Ti–Zr–Pd–Cu–Sn system without Ni element for application as biomaterials. These BMG alloys have a high potential to be applied as metallic biomaterials in various forms, such as melt-spun ribbons and cylindrical rods with a diameter of 4 mm. We also investigated of new Ti-based BMG alloys with higher glass-forming ability (GFA) for medical market as dental implants. These Ti-based BMG alloys do not contain Ni, Al and Be elements which are well known to be harmful for human body. In particular, a rod sample of the Ti_44.1Zr_9.8Pd_9.8Cu_30.38Sn_3.92Nb₂ BMG alloy with a diameter of 3 mm produced by copper mold casting exhibits a compressive strength of 1990 MPa and a Young's modulus of 99 GPa. In addition, the Ti_44.1Zr_9.8Pd_9.8Cu_30.38Sn_3.92Nb₂ BMG shows a large supercooled liquid region of 62 K and a reduced glass-transition temperature, T_rg( = T_g / T_m) of 0.61. The high thermal stability of the supercooled liquid allowed the fabrication of cylindrical rod specimens up to 5 mm in diameter. Thus the studied alloy exhibits high glass-forming ability (GFA) and a large size enough to be used for dental implants. The Ti_44.1Zr_9.8Pd_9.8Cu_30.38Sn_3.92Nb₂ BMG alloy also has a high corrosion resistance and is passivated at the lower passive current density of approximately 10^? 2 A m^? 2, 10^? 3 A m^? 2 and 10^? 2 A m^? 2, in 1 mass% lactic acid, PBS (phosphate-buffered saline without calcium and magnesium salts solution) and HBSS (Hank's balance salt solution without calcium, magnesium and phenol red), respectively, at 310 K, which are lower than those of pure Titanium and Ti–6Al–4V alloy.     

Influence of thermal treatment on microstructure,mechanical and degradation properties of Zn–3Mg alloy as potential biodegradable implant material

In this study, the influence of homogenisation heat treatment effect on Zn–3Mg alloy proposed for biodegradable bone implants was investigated. The alloy was developed via casting process from high purity raw materials and homogenised at 360 °C for 15 h followed by water quenching. Results revealed that the microstructure of as cast alloy was composed of dendritic structure of Zn-rich phase distributed in segregated pattern within Mg₂Zn₁₁ eutectic phase. Exposure to the long duration heating of homogenisation apparently broke the dendrites and transformed them into connected precipitates within the alloy's matrix. Non-equilibrium thermal analysis revealed the formation of Mg₂Zn₁₁ eutectic phase which nucleated at 367 °C and solidified completely at 354 °C. The eutectic coherency point occurred at 368 °C and 424 s when 30% of solid has precipitated during solidification. Homogenisation resulted into lowering the alloy's tensile strength from 104 MPa to 88 MPa but improving elongation at fracture from 2.3% to 8.8%. The homogenised Zn–3Mg alloy showed improved corrosion resistance (corrosion rate = 0.13 mmpy) compared to the as-cast one (corrosion rate = 0.21 mmpy). The mechanical property and corrosion behaviour of the homogenised alloy seem suitable for biodegradable implant applications.     

Effect of anisotropy on fatigue properties of 2198 Al–Li plates joined by friction stir welding

Al–Li alloys are characterized by a strong anisotropy in mechanical and microstructural properties with respect to the rolling direction. In the present paper, 4 mm sheets of 2198 Al–Li alloy were joined via friction stir welding (FSW) by employing a rotating speed of 1000 mm/min and a welding speed of 80 mm/min in parallel and orthogonal direction with respect to the rolling one. The joints mechanical properties were evaluated by means of tensile tests at room temperature. In addition, fatigue tests were performed by using a resonant electro-mechanical testing machine under constant amplitude control up to 250 Hz sinusoidal loading. The fatigue tests were conducted in axial control mode with R = σ_min/σ_max = 0.33, for all the welding and rotating speeds used in the present study.     

Compression properties at different loading directions of as-extruded Mg–9RY–4Zn (RY: Y-rich misch metal) alloy with long period stacking ordered phase

The compression properties at different loading directions of as-extruded Mg–9RY–4Zn alloy with long period stacking ordered (LPSO) phase were investigated. The compressive yield strength (σ_0.2), ultimate compressive strength (σ) and elongation to failure (ε) are 272 MPa, 520 MPa and 19% at ED, 172 MPa, 412 MPa and 17% at TD, and 150 MPa, 370 MPa and 16% at 45° orientation, respectively. The excellent compression properties result from the 14H LPSO strips and random oriented DRX grains with 14H LPSO lamellae. Meanwhile, the as-extruded Mg–9RY–4Zn alloy exhibits obvious mechanical anisotropy. The strength at ED is much higher than that at 45° orientation. Specific to the present alloy, besides the weak basal texture, it is considered that the LPSO long strips with characteristic orientation play an important role in influencing the mechanical anisotropy.     

Effects of Zr and B on the structure and tensile properties of Al–20%Mg alloy

In current research, the effects of different Zr and B contents on the structure and tensile properties of Al–20%Mg alloy have been investigated by using Al–15Zr and Al–8B master alloys. Optical and scanning electron microscopy (SEM) were utilized to study the microstructures and fracture surfaces. Microstructural analysis of the cast alloy showed dendrites of primary α-phase within the eutectic matrix which consists of β-Al₃Mg₂ intermetallic and α-solid solution. After tensile testing, the optimum amounts for both Zr and B were found to be 0.5 wt.%. Ultimate tensile strength (UTS) value of the unrefined alloy increased from 168 MPa to 243 MPa and 236 MPa by adding 0.5% Zr and 0.5%B, respectively. The main mechanism for UTS enhancement was found to be due to the refinement of grains and also altering large dendrites of Al(α)-phase to finer structure. The study of fracture faces revealed that B/Zr addition changes the mode of fracture from brittle to rather ductile.     

Effects of Si addition on mechanical properties and superelasticity of Ti–7.5Nb–4Mo–2Sn shape memory alloy

Effects of 0–2.1 at.% Si additions on microstructure and mechanical properties of a Ni-free biomedical superelastic β-Ti alloy, Ti–7.5 at.%Nb–4 at.%Mo–2 at.% Sn (Ti–7.5Nb–4Mo–2Sn), were investigated. The alloys after annealing at 973 K mainly contain β and α″. As the concentration of Si is higher than 1 at.%, Ti₅Si₃ particles can be found in the alloys, and the number density of the particles increases with the increasing of silicon’s concentration. The addition of Si promotes the strength of the Ti–7.5Nb–4Mo–2Sn due to the Si solid solution strengthening effect and fine Ti₅Si₃ precipitates. However, as the Si concentration reaches 2.1%, the alloy exhibits a brittle fracture. The 0.5–1.6 at.% Si additions improve the superelasticity of the Ti–7.5Nb–4Mo–2Sn alloy by increasing the critical stress for inducing martensite (σ_SIM).     

Effect of impact force on Ti–10Mo alloy powder compaction by high velocity compaction technique

Ti–10Mo alloy powder were compressed by high velocity compaction (HVC) in a cylinderical form of height/diameter (h/d) in die 0.56 (sample A) and 0.8 (sample B). Compactions were conducted to determine the effect of impact force per unit area of powder filled in die for densification and mechanical properties of Ti–10Mo samples. The micro structural characterization of samples were performed by scanning electron microscope (SEM). The mechanical properties of the compressed samples such as Vickers hardness, bending strength, and tensile strength were measured. Experimental results showed that the density and mechanical properties of sample A and sample B increased gradually with an increase in impact force and decreased with an increase in height/diameter ratio. The relative green density for sample A reached up to 90.86% at impact force per unit area 1615 N mm⁻². For sample B, it reached 79.71% at impact force per unit area 1131 N mm⁻². The sintered sample A exhibited a maximum relative density of 99.14%, Vickers hardness of 387 HV, bending strength of 2090.72 MPa, and tensile strength of 749.82 MPa. Sample B revealed a maximum relative sintered density of 97.73%, Vickers hardness of 376 HV, bending strength 1259.94 MPa and tensile strength 450.25 MPa. The spring back of the samples decreased with an increase in impact force.     

Impression creep behavior of a cast MRI153 magnesium alloy

Creep behavior of a cast MRI153 magnesium alloy was investigated using impression creep technique. The tests were carried out under constant punching stress in the range of 360–600 MPa at temperatures between 425 and 490 K. Microstructure of the alloy was composed of α(Mg) matrix phase besides Mg₁₇Al₁₂ and Al₂Ca intermetallic compounds. Stress exponent of minimum creep rate, n, was found to vary between 6.45 and 7. Calculation of the activation energy showed a slight decrease with increasing stress such that the creep activation energy of 115.2 kJ/mol under σ_imp/G = 0.030 decreased to 99.5 kJ/mol under σ_imp/G = 0.040. The obtained stress exponent and activation energy data suggested that the pipe diffusion dislocation climb controlled creep as the dominant mechanism during the creep test.     

Mg–Zn–Y alloys with long-period stacking ordered structure: In vitro assessments of biodegradation behavior

Using Dulbecco's modified eagle medium (DMEM) with 10% fetal bovine serum (FBS) as simulated body fluid, degradation behavior of Mg_100 ? 3x(Zn₁Y₂)_x (1 ≤ x ≤ 3) alloy series with long period stacking order (LPSO) structures was investigated. As indicated, with increasing the volume fraction of LPSO phase, degradation rate of the alloys is accelerated. Further refining the grain size by microalloying with zirconium and warm extrusion has a significant effect to mitigate the degradation rate of the Mg₉₇Zn₁Y₂ alloy. Time-dependent behavior during degradation of the magnesium alloys can be described using an exponential decay function of W_R = exp(a + bt + ct²), where W_R is normalized residual mass/volume of the alloy. A parameter named as degradation half-life period (t_0.5) is suggested to quantitatively assess the degradation rate. For the localized-corrosion controlled alloys, the t_0.5 parameter physically scales with electrochemical response ΔE which is a range between corrosion potential (E_corr) and pitting potential (E_pt). In comparison with conventional engineering magnesium alloys such as the AZ31, WE43, ZK60 and ZX60 alloys, extruded Mg_96.83Zn₁Y₂Zr_0.17 alloy with LPSO structure exhibits a good combination of high mechanical strength, lower biodegradation rate and good biocompatibility.